A fixing device according to the present disclosure includes a rotatable endless belt and an end portion holder. The end portion holder supports each of end portions of the fixing belt rotatably, and has a cylindrical part along which an inner circumferential surface of the fixing belt slides and an end wall part which faces an end surface of the fixing belt. The end wall part has a restraint part which faces an outer circumferential surface of the fixing belt with a predetermined interval and restrains the fixing belt from turning up.